Chitosan Salts

Chitosan carries one stubborn limitation, and it is not the polymer’s fault. The backbone only uncoils in water when its amine groups hold a proton, which is why the base powder sits patiently in a jar until someone adds acid. Whole industries have built their dosing routines around that quirk — acetic acid in the coating kitchen, lactic acid at the filling bench, hydrochloric acid in the treatment plant. A chitosan salt removes the step entirely: the counterion arrives already paired with the amines in the dry powder, so the material walks into plain water on its own.

Eata Marisource supplies the family rather than a single entry — chloride, lactate, glutamate, acetate, formate, succinate, malate and aspartate salts, plus permanently charged quaternary ammonium grades that stay soluble in near-neutral water. Deacetylation runs from the high seventies to above 95%, chain lengths from short polymers under 50 kDa to long ones beyond 800 kDa, and every grade is measured on a fixed method, so the figure on the certificate is the figure in your vessel.

Chitosan salt powder beside the clear solution it forms on its own — no acid dosing step, no vinegar smell in the room.

The Counterion Is the Product

Two salts can start from the same chitosan lot and finish as different materials. Chloride dissociates completely: high charge density, high conductivity, ideal for charge-driven work — and quietly hostile to mild steel. Acetate travels with a volatile partner. As a cast film dries, the acetic acid leaves, the amines take their protons back, and the coating that began water-soluble ends up water-resistant, measurably stronger and a better moisture barrier, with hardly a trace of vinegar left in it. Lactate does the opposite: it refuses to evaporate at ordinary drying temperatures, stays in the film and behaves as an internal plasticiser, which buys you a sheet that gives up some tensile strength but bends instead of cracking. Glutamate holds the solution in a gentle buffered range and has become the default wherever the finished material has to sit against delicate chemistries. Read the anion first; the viscosity figure can wait.

A Menu of Counterions, Not a Shortlist

Every pairing below ships as a standard grade, characterised on the same fixed methods and cut to the same particle windows.

Sulfate sits outside this menu on purpose. Sulfate ions tie chitosan up into insoluble complexes, so no amount of straightforward acid dissolution produces a usable salt — sulfated chitosan exists only as a deliberately reacted derivative, and we quote it separately when a project calls for it.

Manufactured, Not Blended

A salt lot is made, not mixed. Purified chitosan is dispersed, the amines are paired with a stoichiometric amount of the chosen acid, and the resulting solution is dried under vacuum at a temperature that lifts the water without cooking the backbone. That drying step is where a free-flowing powder separates itself from a sticky, partially depolymerised block — the outcome is decided in the oven, not in the bag. Because the pairing is stoichiometric, the free-amine and counterion numbers stay in balance, and the pH we record before packing is the pH you will measure on the bench.

Two quiet limits deserve a place in your trial plan. Dissolved electrolytes screen the charge, so hard or brackish process water pulls the solubility ceiling down even on a well-paired grade. Molecular weight works against you as well: at the same concentration, long chains drop out of solution sooner than short ones.

Vacuum tray drying turns the paired solution into a free-flowing salt powder without overheating the backbone.

Where the Working pH Stops

Every salt in the menu carries a ceiling. Below roughly pH 6 the amines stay protonated and the solution runs clear; push past about 6.5 and the chain loses its charge, collapses and comes back out of solution as a haze or a gum — whichever counterion it happens to be holding. The consequences are practical rather than academic. A chloride grade is a pleasure at pH 4–5 and a filtration headache at pH 7. A quaternary ammonium grade carries a fixed positive charge that ignores pH altogether and stays in solution well into neutral territory, which is precisely why it commands its premium. Check the pH of your process water before you check the price list.

Charge analysis on a finished salt lot — the counterion balance is measured, not assumed.

What the Certificate of a Salt Actually Says

Water-soluble grades are documented differently from the base polymer, and the difference starts with the method. Deacetylation is read by proton NMR under a published standard written for chitosan salts specifically — it covers chloride and glutamate grades across a 50–99% range and calls for a controlled nitrous-acid depolymerisation first, so the sample is mobile enough to yield sharp signals at the elevated analysis temperature. Counterion content is reported straight: on the hydrochloride and glutamate specifications in common catalogue use, chloride is quoted in a 10–20% band, and a result outside that band is telling you how much free acid or free base you also bought.

• Degree of deacetylation by ¹H NMR against the salt-specific method, with an FTIR band-ratio cross-check
• Counterion content plus the free-acid / free-amine balance, so the pairing is verifiable rather than asserted
• Viscosity read in water alone — no acetic acid in the test, because the salt does not need it
• Residual ash ≤ 1% and residual protein ≤ 0.3% on purified cuts
• pH of a 1% solution, typically between 4 and 6
• Moisture and water-insoluble matter — the two numbers that set how fast the powder wets out
• Heavy metals by ICP and a full microbial panel; endotoxin quoted on grades sold for biomaterials and fermentation research

Falling-ball viscometry on a salt solution — viscosity in water, because the salt dissolves without help.

Mill Floors, Dye Houses and Membrane Benches

The salt form earns its keep wherever a process cannot tolerate an acid dump, and that describes more of industry than you might expect.

Paper mills

Cellulose fibres carry a negative surface, which makes a cationic polysaccharide a natural guest in the wet-end. Trials that compared chitosan acetate and hydrochloride against other additives for alkylketene dimer sizing in alkaline papermaking found the salts produced the most pronounced effect on sizing response and AKD retention of anything tested. Beyond sizing, the same affinity shows up as higher dry and wet strength, better retention and drainage, and specialty grades such as antibacterial and greaseproof papers — all achieved at addition levels low enough to leave the furnish pH untouched.

A wet cellulose handsheet lifted from the wire — chitosan salts anchor to fibre surfaces exactly like this one.

Effluent and process water

A treatment plant already running at neutral pH does not want acetic acid added to its balances, and a mild-steel dosing line does not want chloride either — which is why glutamate and lactate grades have found a home there. The charge does the familiar work: anionic dye capture, turbidity and COD reduction, and metal binding by chelation and ion exchange, with copper uptake reported to peak near pH 4 and sorbent particle sizes in the 250–450 µm band giving the best trade between capacity and kinetics.

Textile finishing

Quaternary ammonium grades in particular answer two problems at once. Their fixed charge anchors to cotton and blends for antimicrobial, deodorising and antistatic finishes, and the same cationic character improves dye fixation and colour fastness — a chemistry that displaces formaldehyde-based and fluorinated finishes rather than adding a third problem to the effluent stream.

A padding mangle in a finishing line — the salt solution wets the fabric evenly at a pH the dye house can live with.

Films, coatings and electrolytes

Cast from water, an acetate salt dries into a film that gradually loses its volatile partner and re-hardens; studies following residual acid through the drying cycle report falling water-vapour permeability and moisture content once that acid is gone. Lactate films trade tensile strength for elasticity. Chloride solutions, meanwhile, supply mobile ions inside a hydrated polymer matrix — chitosan-acetate films have shown proton conductivities in the region of 10⁻⁴ S cm⁻¹ when hydrated, which keeps them on the shortlist for membrane and solid-electrolyte research.

Base Polymer or Salt? The Decision in One Table

The salt costs more per kilo than the base polymer, so it should only ever be chosen for a reason. The reasons are narrow and specific.

Salt Work to Order

• Any counterion on the menu, or a pairing we have not listed, provided the acid dissolves cleanly, travels well and dries without residues
• Deacetylation held inside a window rather than quoted as a nominal value
• Viscosity band matched to your pump, mixer or coater
• Chain length cut from below 50 kDa to above 800 kDa
• Quaternary grades with a defined degree of substitution for permanent-charge systems
• Particle cut from 40 to 200 mesh, or milled finer where dispersion speed matters
• Ready-dissolved solutions and concentrates for plants that would rather buy the liquid than make it

Tell us the pH of your process water, the anion your equipment can tolerate and the method your lab actually runs, and we will match a lot against it — then hold that specification across repeat orders instead of drifting back to a catalogue average.

For Research or Industrial Raw Materials, Not For Personal Medical Use!